Wiring schema for converting 4EAT to full-time Power Mode

svxistentialist · #1 08-31-2006, 09:32 AM

Having kicked around the idea of converting US cars to have a switch like JDM cars for activating Power mode full-time, I now have established what way it needs to be wired so you can convert your cars.

I know some of you will be keen to make this conversion, particularly those that have done engine upgrades and still retain the auto gearbox.

I'm going to copy over the relevant posts from Zavikan's thread so you can see where the idea is coming from.

Joe

svxistentialist · #2 08-31-2006, 09:34 AM

I have just done some study on the US wiring diagram vs the Australian one, and I now have almost sorted out how you US guys can wire up permanent Power mode.

The TCU makes its calculations on when to employ Power mode based on input from the TPS. This is a white wire that connects to B67 Pin 8, the smallest connector into the TCU, the 12 pin one.

What we have to do to trick the TCU into switching on the Power mode is to feed this white wire a 4.8 to 5.0 volt signal. The TCU will assume the throttle is wide open, all the time, and will leave Power permanently on.

Next, how do we feed a 5v signal to this line? Well, this is my idea. There are three wires going from the MPFI unit to the TPS, Red, White and Black. The white wire is the variable voltage signal that the TPS returns to the ECU and the TCU. The black wire is the earth. I'm willing to bet that the red wire is a 5V feed from the MPFI unit that the TPS modulates through a resistor.

Now if this red wire is a 5V feed, then what we do is connect a switch between the red wire and the white wire. When the switch is ON, the red 5v wire is fed to the TCU, voila!, full-time Power mode. When the switch is OFF, the white wire is fed to the TCU, and we are back to normal, Power will come on when the demand is beyond the set levels.

I'm willing to bet this will work, and tomorrow I will check the TPS red wire voltage to see if my calculations are correct.

However, we are taking Zavikan's thread way off topic, so when I check the voltage tomorrow, I will put up this how-to in the Technical forum so you guys can do a guinea pig with the wiring, wire in a switch and try the system out.

It will be fun if it works!!

PS I'm also fairly sure that grounding pin 4 will cause the TCU to go to Economy mode, no Power shift map.

svxistentialist · #3 08-31-2006, 09:35 AM

A couple of points.
Joe first I think there Are 3 maps, may be 4, in the TCU. Normal. Power and the one used be the Cruise Control. As our Aussie model does not use the Economy switch, this may be the same map as the cruise map. If it is not, then there are 4 maps.

The other is if you switch the white wire to 5V to hold the Power map, it will also hold the ECU at full throttle signal all the time. You would have to isolate the 5V signal from the ECU, and only allow it to the TCU.

Harvey.
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svxistentialist · #4 08-31-2006, 09:38 AM

The first bit is about 4EAT shift modes. The important bit about the Power mode is in the last paragraph:

Mind mapping!
Quote:
Originally Posted by oab_au
Joe first I think there Are 3 maps, may be 4, in the TCU. Normal. Power and the one used be the Cruise Control. As our Aussie model does not use the Economy switch, this may be the same map as the cruise map. If it is not, then there are 4 maps.

The other is if you switch the white wire to 5V to hold the Power map, it will also hold the ECU at full throttle signal all the time. You would have to isolate the 5V signal from the ECU, and only allow it to the TCU.

Harvey.

Hi Harvey,

I am not so sure you are correct in this, but I think I see what you mean.

What I said was there are only two shift maps in the software, Normal and Power. These two maps determine when the upchanges and downchanges happen depending on a number of inputs, and relating to the demand from the driver.

In the case of the cruise control, this controls the gearbox by the application of a voltage from the cruise control computer to B66 pin 3. When cruise is ON, this voltage is <1 volt. When OFF, it is variable from 6 to 10.[interesting that it is over 5 v, the range which reads the TPS, is it not?]

What Econ does is deny the use of the Power shift map, so I'm saying it is not a shift map in itself, just a blocking circuitry.

Likewise with the cruise control. It does not redetermine shift points. It merely sets parameters for steady speed driving conditions, and for over-ride of these conditions, but using the Normal shift control map. It may also deny access to the Power shift map, that would seem to make sense too, but I'm only guessing on that.

Spot on agreement on your last point. The variable feed voltage on the white wire has to be fed at all times to the ECU. The divert we make is only to the TCU feed, B67 pin 8. We feed it variable voltage for "on demand" Power mode availability, and steady 5 v for full-time Power mode. The ECU will not be affected, it will be reading the throttle position requirement through the white wire variable voltage feed on B60 pin 2.

Joe

PS Strange you Aussies did not get the Econ switch. The wiring for it is shown on the diagram you sent me!

svxistentialist · #5 08-31-2006, 09:45 AM

OK guys, I have checked on the wiring, and the voltages are as I surmised from looking at the wiring diagrams.

Essentially, there are three wires to the TPS as many of you know. The black one is an earth, the red one is a 5v feed to the TPS from the ECU, and the white centre one is the variable voltage signal wire out from the TPS. This feeds back to the ECU so the ECU can make calculations based on how fast and how far the throttle is opened, and manage the fuelling accordingly.

There is a white wire tapped from this feed to the ECU that goes to the TCU at B67, pin 8. Your TCUs in the US are set up the same as the UK and Euro versions. It will assess how much demand for overtaking speed is required, and switch on the Power mode map if beyond certain parameters.

When this Pin 8 gets the full voltage, about 5v at WOT, then Power mode is engaged.

To be continued...

svxistentialist · #6 08-31-2006, 10:27 AM

Next stage:.......

What we plan to do is feed Pin 8 B67 the full 5v signal so that the TCU assumes we are on WOT all the time, and leaves the Power mode shift map switched on.

The way to do this is really simple. We need to tap into the 5v feed that the ECU is sending to the Throttle Position Sensor, and feed this voltage to Pin 8 B67 of the TCU, rather than show it the variable voltage of the white wire from the TPS already feeding Pin 8.

Now if you simply disconnect[ cut] the white wire from Pin 8 B67, tap into the red wire 5v feed from the ECU out of B60 pin 3, and connect this to Pin 8 B67, you now have Permanent Power mode. And I mean permanent in the sense that you can't switch it off. If you are unhappy with it for any reason, then you will have to reverse the wiring, connect back in the white variable voltage wire to Pin 8 again.

Of course, it would be better to have it like the Japanese do it, so we can switch on the Power mode if we want to rock and roll, or switch back to Normal mode if we want smooth shifts and chill out listening to Barry Manilow.

Hey, I know you guys all listen to Barry Manilow when no one's around, so don't try and deny it!

Next stage, switching it on and off.